1. Field of the Invention
The present invention relates to a liquid container. More specifically, the present invention relates to a liquid container used in a configuration to detect information on a state of the liquid container (such as information on residual quantity in an ink tank used for ink jet printing), by use of light emitting means such as a light emitting diode (LED). The present invention also relates to a liquid container system and a printing apparatus using the liquid container, and to a circuit board for the liquid container.
2. Description of the Related Art
Performances of ink jet heads are dramatically improved in recent years along with increasing demands for higher resolution and higher image quality printing. Specifically, printing speed and printing throughput are improved by increasing the number of ejection ports and energy generating elements in a printing head or by increasing the number of energy generating elements to be operated simultaneously.
In order to learn the lifetime or appropriate time for replacing such a high-performance printing head, Japanese Patent Application Laid-open No. 7-76104 (1995) discloses a configuration in which an ink jet head 1105 includes a memory element such as an electrically erasable programmable read-only memory (EEPROM) for storing specific information on the ink jet head 1105.
FIG. 28 is an explanatory view of this configuration. In the configuration of the drawing, electric signal lines from the printing head 1105 provided with an EEPROM 1108 essentially consist of lines 1106(a) to 1106(c). These lines are extended from connectors 1028 on the printing head 1105 to flexible cables 1206, and are connected to a central processing unit (CPU) 1300 of a control circuit portion of a printing apparatus body.
Further, there is also a technique configured to embed a memory element for storing information on residual quantity and the like on each ink cartridge so as to display the information on a printing apparatus body's side.
FIGS. 29 and 30 are explanatory views showing examples of the above-described two configurations. In the configuration shown in FIG. 29, a plurality of ink cartridges, which correspond to inks of four colors, 1001K, 1001Y, 1001M, and 1001C embed memory elements 1100A, 1100B, 1100C, and 110D, respectively. Signal lines for these memory elements are bundled on the printing head 1105 together with signal lines for the memory element 1018. The group of the signal lines 1016 is extended from the connectors 1028 on the printing head 1105 to the flexible cables 1206, and is connected to the CPU 1300 of the control circuit portion of the printing apparatus body. Meanwhile, in the configuration shown in FIG. 30, the memory elements 1100A to 1000D capable of storing various pieces of information are directly connected to the CPU 1300 of the control circuit portion of the printing apparatus body without passing through the printing head 1105. In this way, the CPU 1300 can perform suitable operation control based on the direct connection.
As described above, there are various configurations in terms of electric connection between the memory elements, which are arranged on the printing head and on the ink cartridges, and the printing apparatus body in conformity with the structure of the printing apparatus.
The ink has been also improved in recent years to achieve the above-described high-definition printing. Specifically, the ink including components with extremely complicated and delicate composition ratios in consideration of various characteristics is used for achieving a high printing performance. Moreover, the improved ink has been used. For example, such the improved ink may contain pigment components instead of dyestuff components in order to enhance weather resistance of the ink or fastness of a printed image. Meanwhile, a resin component may be added to the ink for promoting fastness to achieve higher speed. Moreover, the ink may include a composition blended on the assumption that ink components for respective colors are subjected to chemical reactions in the case of multicolor printing. In addition, the type of the ink may be changed in response to the quality of a printing material (such as dedicated paper for ink jet printing, plain paper, a resin sheet or a cloth) or in response to an intended visual effect (presence or absence of gloss, the use of gold and silver colors, and the like).
As described above, the improvement in higher printing quality is attempted by use of the ink having the components or the composition ratios different from those of conventional ink. When only the same type of the improved ink is used in a printing apparatus, the printing apparatus can operate without any problem and perform high-definition printing while exploiting the performance of the ink. On the contrary, in the case of using different types of the ink alternately in the single printing apparatus, the following obstacle may arise when the printing apparatus is particularly configured to allow attachment of a plurality of ink cartridges to a single ink jet head including a plurality of ejection portions. Specifically, the different types of ink are mixed together inside the single ejection portion, and lead to aggregation or solidification attributable to a reaction between the ink components and eventually to deposition of the ink onto an ink supply path inside the ejection portion, a fluid path inside an ejection opening or a surface (an ejection surface) of the printing head where the ejection openings are formed. When such an obstacle arises, a printing operation will be hindered. Accordingly, it is necessary to make an arrangement to avoid mixture of the different types of the ink inside the printing apparatus. In this context, it is strongly recommended to configure the printing apparatus not to connect an ejection portion that corresponds to a certain type of ink to an ink cartridge that contains a different type of ink.
A first method of solving such an obstacle is to use an ink cartridge in a different shape depending on the type of the ink and to eliminate compatibility between ink cartridges configured to contain different types of the ink. In this case, however, the ink cartridges have disadvantages of a tremendous increase in manufacturing costs and complication to store and manage the ink cartridges having the different shapes.
On the contrary, the configuration provided with the memory elements 1100A to 1100D for storing data representing the types of the ink contained in the respective ink cartridges 1001K to 1001C as shown in FIG. 29 or FIG. 30 is effective as a second method. For example, Japanese Patent Application Laid-open No. 6-155769 (1994) discloses a configuration in which a memory element of an ink cartridge is connected to an electric circuit of a printing apparatus body so that the type of the ink can be identified by use of a difference in a voltage value. Meanwhile, Japanese Patent Application Laid-open No. 2000-301738 discloses a configuration in which a control IC of a printing apparatus body is connected to a memory element which stores data indicating the type of ink contained therein, manufacturing date, and the like. The control IC then reads and writes the data. Here, it is possible to prevent occurrence of the above-described obstacle by detecting connection of an ink cartridge containing a certain type of ink to an ejection portion corresponding to a different type of ink based on the information on the ink cartridge's side and informing a user of an event of improper connection.
As described above, Japanese Patent Application Laid-open Nos. 6-155769 (1994) and 2000-301738 disclose the configurations in which ink cartridges 1001K to 1001C respectively store the information on the types of the ink contained therein, residual quantity thereof, expiration dates, and the like. Meanwhile, Japanese Patent Application Laid-open No. 7-076104 (1995) discloses a configuration in which information on an identification number of the printing head 1105, the total number of prints, and the like is stored in the memory element 1018 embedded in the printing head 1105. By a combination of these configurations, the CPU 1300 of the printing apparatus body can identify the ink cartridges 1001K to 1001C and the types of the ink contained therein by reading the information respectively out of the memory element 1018 and 1100A to 1100D. In addition, the CPU 1300 can determine lifetime and replacement timing of the printing head 1105 and of the ink cartridges 1001A to 1001D appropriately. Moreover, it is also possible to execute fine printing by setting optimal printing conditions corresponding to the ink and conditions for a recovery process for optimizing an ink ejection performance of the printing head.
In addition, Japanese Patent Application Laid-open No.4-275156 (1992) discloses another configuration for appropriately informing the lifetime and replacement timing of the printing head 1105 and of the ink cartridges 1001A to 1001D appropriately. Specifically, in this configuration, a cartridge formed by integrating a printing head and an ink tank includes a light emitting portion in the form of a light emitting diode (LED). Here, it is possible to inform ink residual quantity in response to information from a memory element storing the number of power distribution to the cartridge for printing.
When using the configuration disclosed in Japanese Patent Application Laid-open No. 4-275156 (1992), it is desirable to continue display until immediately before a user replaces the ink tank so that the user can execute the operation to replace the ink tank without causing an error. When the ink cartridge subject to replacement is displayed by means of light emission, such display will largely contribute to an easier replacing operation by the user. In this case, the user is supposed to detach the ink cartridge including the LED emitting the light.
Here, Japanese Patent Application Laid-open No. 4-275156(1992) only discloses the state where ink tank provided with an indicator is attached to a printer body. However, when considering that the ink tank is rendered detachable from the printer body, it is conceivable that this configuration is assumed to adopt a configuration of connection similar to those disclosed in Japanese Patent Application Laid-open No. 7-076104 (1995) and 2000-301728, and that power is supplied from the printer's side to the indicator and the memory in the attached state.
Therefore, replacement in the displayed state is equivalent to detachment in the state of connecting a power source and a communication line, which is so-called hot-swap. The memory is usually a semiconductor element which is manufactured by use of delicate processes and is operated based on a well-managed power source. For this reason, if the ink tank is detached from the printing apparatus body during access to the memory and the communication line is suddenly shut down, there is a risk of destruction of not only the information stored in the memory but also the memory in itself depending on the type or the processes of the memory element.
Here, a case of performing information in conformity with the ink residual quantity of each of the cartridges by use of the light emitting element disclosed in Japanese Patent Application Laid-open No. 4-275156 (1992) is considered. The ink residual quantity can be detected for instance by causing a main control portion of the printing apparatus to count the number of dot printing in the course of printing control and to subtract the counted value from a numerical value corresponding to an initial content of the ink. In this case, the main control portion judges loq ink residual quantity and informs that fact to the user when the calculated value becomes equal to or below a predetermined proportion relative to the initial content of the ink. At the same time, this information is written in the memory. The process performed at this time is to transmit commands corresponding to the ink residual quantity to a circuit board on the ink cartridge inclusive of the memory, the LED, and the like. These commands include a command to update the ink residual quantity by reading and writing the memory (memory access), a command to start display by driving the LED in conformity with the information, and the like.
In this configuration, when the number of the ink cartridges is increased, more memory access commands and drive control commands for the LEDs will be transmitted on the lines. As a consequence, when the residual quantity varies among the ink cartridges, those commands will be transmitted frequently. In this way, along with the increase in the opportunities of memory access, there is a growing possibility of destruction of the contents stored in the memories due to the characteristic of power shutdown sequences caused by the hot-swap.
In particular, the memory stores a variety of important information besides the ink residual quantity, namely, information on the color of the ink contained therein, manufacturing information on the ink cartridge such as a specific number or a manufacturing lot number, and the like. In this regard, the memory is typically formed of a non-volatile memory element so that the memory can retain the stored contents even when the power is not supplied thereto (in the state where the ink cartridge is not attached to the printing apparatus). Therefore, if the stored contents are destroyed and it is not possible to make reference to the important information such as the information on the ink residual quantity which is constantly updated, the function of the printing apparatus to detect the ink residual quantity will not be operated normally. As a consequence, the ink may run out in the course of printing, and the printing apparatus may fail to offer high-quality prints as requested by the user.
Accordingly, it is conceivable to shut down the power safely at the time of an operation by the user to take place before the ink replacing operation, such as an operation by the user for opening a cover or the like provided on the printer body. However, the indicator will be also turned off in this case, and it will be uncertain as to which ink tank is subject to replacement. As a result, the advantage of the configuration to provide the indicator will be lost.
In addition, another problem of the conventional technique derives from the configuration of the connectors.
For example, the following problem arises when the memory elements for storing the variety of information including the ink type are mounted on the ink cartridges in addition to mounting the memory element 1018 on the printing head 1105. Specifically, in this case, it is necessary to electrically connect all the memory elements to the CPU 1300 of the control circuit portion of the printing apparatus body. Therefore, when the number of the memory elements is increased, the number of the signal lines 1016 required for connecting the memory elements is also increased.
Particularly, it is conceivable that even a low-price printing apparatus applies various types of ink in recent years. For this reason, connectors for connecting the memory elements respectively provided on the printing head and on the plurality of ink cartridges to the CPU 1300 of the control circuit portion of the printing apparatus body are equipped. Typical color printing applies ink in four colors (black, yellow, magenta, and cyan). Accordingly, four ink cartridges 1001K, 1001Y, 100M, and 1001C respectively containing the respective colors of ink are simultaneously attached to the printing apparatus body. Therefore, the four memory elements 1100A to 1100D provided on the respective ink cartridges 1001K, 1001Y, 100M, and 1000C require the signal lines 1016. Usually, each memory element is provided with two or more signal lines 1016. Meanwhile, when the printing head 1105 is also provided with the memory element 1018, it is necessary to provide three signal lines 1016, for example, in addition to the signal lines 1016 connected to the memory elements on the respective ink cartridges.
As a result, when connecting all the signal lines to the CPU 1300 through the printing head 1105 as shown in FIG. 29, it is necessary to provide the signal lines 1106 at least twice as many as the total number of the memory elements. The requirements also apply to the case shown in FIG. 30 where the memory element 1018 of the printing head 1105 and the memory elements 1100A to 1000D of the respective ink cartridges 1001K, 1001Y, 1001M, and 1001C are directly connected to the CPU 1300.
In addition, in the case of the configuration as disclosed in Japanese Patent Application Laid-open No. 4-275156 (1992) where each of the ink cartridges includes informing means and the ink residual quantity is informed by use the informing means, it is also necessary to provide a line to turn the informing means on and off. Here, each ink cartridge requires at least one line without considering a ground line. In other words, four or more signal lines are required in the case of using four or more ink cartridges to perform color printing. In this way, the number of connection to the printing apparatus will be further increased.